MEMOIR OF STURGEON. H5 



determine the temperature of a body moving through 

 the air, and so to prove the assumption involved in Joule's 

 explanation of shooting stars, viz., that a body moving 

 through the air would be raised to a temperature greater 

 than that of the air through which it is moving. 

 Although this assumption is in strict accordance with 

 thermo-dynamics, and as applied to such velocities as those 

 of meteorites, may pass without appearing contrary to 

 experience ; yet to say that a body placed in a high wind, 

 or whirled through still air, will have its temperature raised 

 above that of the air, does seem paradoxical and against 

 ordinary experience. The research, however, which was 

 continued till the end of 1859, completely confirmed the 

 assumption, a thermometer moving at 100 miles an hour 

 being raised some 2° Fah., and the temperature increasing 

 with the square of the velocity ; so that this rise was quite 

 sufficient to account for the meteoric effects of bodies 

 moving at 19 miles a second. 



These investigations appear to be the only experimental 

 work undertaken by Joule between 1854 and 1857 ; but, in 

 1856, he wrote the account of Sturgeon, published in the 

 Society's Memoirs, Vol. XIV., second series. In this 

 "Memoir" Joule reproduces the vindication which he had 

 previously written of Sturgeon's claim to be the discoverer 

 of the soft iron electro -magnet and electro -magnetic engine, 

 and the " commutator :" 



In 1857, Joule had commenced his very important 

 researches " On the Thermal effects of stretching and com- 

 pressing Solids," " On compressing Liquids," and " On some 

 Thermo-dynamic Properties of Solids." 



These researches, though conducted by Joule, appear 

 to have been largely suggested by Sir William Thomson's 

 L 



